A number of performers and teachers have commented in the past about trumpet playing being physical. Some say it is all in the air. Others claim that it is 90% mental. All of these are correct.
To play a long gig 6 nights a week is demanding physically and mentally.

The physical aspect we hope is taken care of by years of preparation ( practice ). There are almost as many ideas about creating endurance as there are trumpet teachers yet they tend to share the same basic concept. That concept is to build your strength a little at a time by adding a little more work. This is like running a marathon you start out by going 1 block. You add distance to this as you can . Now playing a pro gig is the marathon. If you have never done this distance in practice then you are in for a difficult time.

Jacoby used to talk about reserve power. He would have a new student place his hand on his stomach and sing a second line g.   9 out of 10 do this with no tensing of the muscles at all. Yet went asked to play that same g these people ( me included ) tensed up. This is power that could be saved and used later in the job. Normal muscle tension and outside air pressure will produce a good clear tone on notes under 4th space e. ( + or - a note or 2 for physical differences ) This simple concept adds reserve power to your playing.  Other reserves are available in the chops as well. In playing the Stevens learning to make a cushion by pushing your entire embouchure forward creates a reserve. In the Farkas learning to pivot correctly to release the pressure off of your top lip adds reserve.

Air is free use all you want. Those of you who walk or run practice timed breathing while doing this. The practice will help you to control your breathing when the jobs roll around and the tension gets going.

Mental reserve is the difficult part. Years ago Doc mentioned that he was really into zen. He described how he tried to picture himself as the note that he was playing. He mentally followed the progress from breathing, turn around, compression, rushing past the lips, through the horn all of the way to the back of the hall he was playing in. This kept his mind busy on what was important and left no time for nerves.

'Pops'

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http://www.webfeats.com/btc/trumpet.html